The present invention relates to nozzles for aerating a relatively low pressure liquid stream to produce a sprayable foam, and more particularly, to a nozzle assembly which permits ready interchangeability of a nozzle tip for creating different foam spray application patterns.
Foams are typically produced by the mixing of a chemical, water and a gas under certain conditions. The particular chemicals employed depends upon the desired use of the foam. For example, in the agricultural arena foams are often used to apply pesticides and are often preferable to liquid application.
The application of chemicals in a foamed condition offers a number of benefits. The foam application permits the chemicals to be used with lower supply rates and active chemical content, thereby reducing costs. Further, the use of a foam composition reduces health and safety hazards caused by the splashing or drift of tiny droplets or a fine mist. Because a foam is readily visible it also provides a convenient way for visually determining coverage.
Generally, two basic methods have been utilized to generate foams. One method is the use of a chemical foaming agent which is added to the solution, and the solution is then foamed. The other method is the introduction of gas such as air into the liquid to form minute bubbles, thereby collectively forming the foam. The application of agricultural chemicals by foam generating equipment traditionally includes a nozzle unit which mixes air with liquid chemicals.
The type and consistency of foam created by particular foam generating nozzles is a function of a number of factors, including the chemicals to be applied, the pressure of the material when applied to the nozzle unit and the design of the nozzle unit. A resulting consistency of the foam is often dictated by the anticipated application. That is, for applications requiring prolonged retention on a vertical or downward facing surface, it is usually desirable to apply the material as a thick foam. Such foams often follow a 1:10 ratio, that is for each unit volume of liquid, 10 unit volumes of foam are produced. Alternatively, if penetration of a porous surface is desired, the foam is preferably formed with a minimally sized bubbles in a ratio of approximately 1:2.
It has been found that at the relatively low operating pressures, it is difficult to obtain sufficiently small particle size and hence sprayable foam generation. Therefore, prior systems have relied upon relatively high fluid pressures for foam generation. The prior foam generating devices are relatively high pressure units requiring 40 psi or more. The mechanisms required to generate these relatively high pressures and the inability of the foaming nozzles to efficiently use the available energy at low pressures have prevented relatively low pressure foaming technology in a truly portable, human transportable foaming apparatus.
Further, in view of the relatively complicated structure required for the passage of a liquid, introduction of air, generation of foam and application of the foam, a given foaming nozzle unit traditionally creates only a single type foam. That is, if alternative chemical compositions, or application patterns are desired, the nozzle unit must be completely removed and an entirely new nozzle unit applied. This increases the cost of the foam applicators.
Therefore, a need exists for a foaming nozzle assembly which is easily reconfigured to create a variety of foams. Further, the need exists for a foam generating nozzle which may be readily disassembled, cleaned and reassembled. The need also exists for such a nozzle assembly which may be reconfigured with interchangeable components. A similar need exists for a foaming nozzle assembly that can employ interchangeable nozzle tips or be constructed at cost that allows interchangeability. A further need exists for a foam generating nozzle that can be used in relatively low pressure applications, such as less than approximately 35 psi and still generate sufficient quantities of foam.
The present invention provides a foaming nozzle assembly for generating a sprayable foam at relatively low fluid pressures, below approximately 35 psi. Preferably, the foaming nozzle produces foam at pressures as low as 25 psi. The present foaming nozzle assembly may be readily attached to a wand. The foaming nozzle may also be disconnected from the wand and disassembled to allow for the ready interchangeability of the components, including a nozzle tip. Thus, the present invention allows a modification of the foam characteristics and application pattern without requiring the use of an entirely new assembly. The sprayable foam formed by the present foaming nozzle assembly reduces wind drift, lowers the required chemical concentration and allows for visual confirmation of both the spray path and the treated areas.
Generally, the present foaming nozzle assembly includes an elongate housing with a first end configured to releasably engage a conduit or wand, and a second end defining an outlet aperture. The housing further includes a stop and a radially directed air inlet port. The foaming nozzle assembly further includes a nozzle tip having a shoulder for cooperatively engaging the stop. The nozzle tip is constructed to be slideably disposed within the housing from the first end so as to seat against the stop and substantially occlude the outlet aperture. The foaming nozzle assembly further includes a throat having a divergent end and a convergent end, the throat being sized to be slideably disposed within the housing and contact the divergent end with the nozzle tip. Finally, the foaming nozzle assembly includes a venturi nozzle/deflector sized to be disposed within the housing such that the deflector portion operably aligns with the air inlet port in the housing and the venturi nozzle/deflector contacts the convergent end of the throat.
In an alternative configuration, the foaming nozzle assembly is constructed of two pieces. The two piece design may be formed in at least two configurations. In a first configuration of the two piece design, the foaming nozzle assembly is constructed of a flow body and a nozzle tip. The flow body includes structure corresponding to the venturi nozzle/deflector, the throat and a portion of the housing of the first embodiment. The flow body is an integrally formed single piece construction that includes structure corresponding to the venturi nozzle/deflector, the throat and a portion of the housing of the first embodiment. The nozzle tip is mechanically engaged the flow body to control the desired spray pattern and assist with foam generation. As the nozzle tip can be releasably attached to the flow body, the nozzle tip can be readily interchanged without requiring extensive downtime.
In the second configuration of the two piece embodiment, the foaming nozzle assembly is formed of mating halves along the flow path or longitudinal axis of the assembly. That is, each mating half includes a portion of the housing, the venturi nozzle/deflector, the throat and the nozzle tip. In this construction, the nozzle tips are not interchangeable with the remainder of the foaming nozzle assembly, but rather the entire foaming nozzle assembly is readily interchangeable with respect to the wand.
The present invention also contemplates a method of assembling a foaming nozzle assembly including slideably disposing a nozzle tip within an elongate housing, such that motion of the nozzle tip through the housing is limited by contact between the nozzle tip and the housing; disposing a diverging throat within the housing to be operably disposed with respect to the nozzle tip; disposing a venturi nozzle/deflector within the housing to operably align with the throat, thereby providing fluid communication through the venturi nozzle/deflector, the throat and the nozzle tip, and providing fluid access from a radial port in the housing to a convergent end of the throat.
Alternatively, the present invention contemplates a method of assembling a foaming nozzle assembly by engaging a nozzle tip with a body having a venturi nozzle/deflector and a throat to define a flow path therethrough. A further method encompasses assembling a foaming nozzle assembly by mating a pair of assembly halves, each half including a portion of a venturi nozzle/deflector, a throat and a nozzle tip.